1. Field of the Invention
This invention relates to a roof structure and, more specifically, to such a roof structure which includes several layers of heat resistant material.
2. Description of the Prior Art
It is not uncommon for a roof structure to be formed of several courses or layers of bricks which have heat resistant characteristics. The roof structure is located basically in an opening which is between and defined by the upper ends of the side walls of structure. The following sequence is frequently used to provide such a roof structure having heat resistant qualities. The bottommost layer of silica brick is laid in the lower part of the opening between the side walls and supported thereby. A layer of standard fireclay brick is laid over the silicon brick layer. The next layer would include lightweight refractory brick. A layer of standard insulating brick would then be laid on top of the lightweight refractory brick. Finally, the uppermost layer of the roof structure is formed by common red brick.
Although such roof structures have been employed in the past, it has always been recognized that the manufacture of heat resistant or refractory bricks of this type is very expensive. The expense of the refractory bricks is primarily due to the fact that so many special shapes are required. The special shapes are needed to insure proper integrity of the roof structure throughout extended use. In fact, it has also been found that the need for such integrity has significantly added to the design costs of providing such a roof structure because of the need to specifically design each of the many special shapes of refractory bricks. In addition to the design costs, the requirement for many shapes of the refractory bricks significantly extends the overall design-to-completion time. Since each of the different shapes must be specifically produced, the increased manufacturing time can significantly add to the overall cost of the project of providing the desired roof structure. Finally, when the refractory bricks are available, the actual assembly costs are elevated because of the additional labor time and skill required to assemble the roof structure with the refractory bricks having different shapes.
Even with such design requirements and care in assembly, there is a continuing concern that roof structures formed of such refractory brick will be susceptible to gas penetration after initial assembly and throughout extended use of the roof structure. Accordingly, any type of roof structure which can reduce the design, manufacture and assembly expenses and which would tend to remain more effective for preventing penetration of gas would clearly be desirable.